Curved Small Thor Build

[Renron]

Firstly I want to thank EVERYONE who has contributed their time and MEGA brainpower to make the Thor a competent platform.

I am building a curved small Thor gleaned from the hard work of many contributors. I have attached a few pictures of my progress.

Question(s) to those with experience in such things;

1) Is it necessary to compensate for the lost interior cabinet volume due to the semi curved back side? If so, can I increase the cabinet depth by adding another front baffle with the appropriate amount of material removed to equal the lost interior volume? (similar to cutting "H" braces) it's ~141 cu. inches

2) Should I add additional weight to the cabinet? What is the purpose of additional weight? Prevent speaker roaming? Ala Subwoofers?

3) I've called the owner of Piano-Lac and he no longer sells to us DIY'ers unless a commercial address is available for shipping. He stated he had a problem with liability issues. I don't know anyone with a commercial address where he can ship to COD. Any Ideas?

4) Any problems with rubber feet on the bottom of the cabinets instead of spikes? I have laminate floors on a raised foundation.

Man, That MDF makes a mess!

Thanks for your help.
Ron

[planet10]

A whole lot of swiss cheese there. Cool.

Yes, you should try to maintain the volume.

dave

[Renron]

Strappin' down those wild beasties....ummm no.
As expected I made a mistake here in this photo. Yep. It's not placing the straps directly over the internal bracing. Caused the cabinet sides to warp! I was able to correct this faux-pas by cutting spacer blocks 3/16 wider than the internal diameter and forcing (spreading) the sides apart. Learning as we go.

I have 2 layers of 3/8 bendy ply on the cabinets now and used copious amounts of gue on both sides of the lay-up. Shot the ply down with 1" pin nails ... a little long but will not bother anything down the road. The bendy ply was a touch on the rough side (looks like resawn lumber) so I am adding a 1/8" skin on top of the existing plywood sides. The 1/8 ply is also bendy ply buy has a VERY smooth exterior to mate with the cherry veneer that will 'Purdy -em up. I'll post more pics again when I complete the next stage(s).
Ron

[Renron]

A knot in the verticle spine caused a slight bend in the cabinet shape near the top, this was cured by relieving some tension on the inside of the bend. This method works well, and straightened it out overnight. Wood is not ever perfect. So we do our best.

Ron

[Norman Tracy]

Renron,

Looking good!

For your finish you might want to look into CrystaLac. They have a gloss & satin black system. I have not tried their black system, their gloss clear poly is very nice. Builds quickly, mistakes rework well, and the gloss is simply up to how much wet sand/polishing time you want to invest.

Mail order source:
http://www.mcfeelys.com/subcat.asp?sid=42

The CrystaLac system coms in both brushable and spray on types. The black system appears to be spray on only. Of course regardless of what you settle on some expermenting on something you have less time in is called for.

[planet10]

Hi Norm,

Nice to see you hanging around....

I've sent you mail...

dave

[Renron]

Thanks Norm,

I buy screws from McFeeleys' all the time, as I am a General Contractor and do a lot of repairs. I love their square drive cabinet screws, haven't broken one yet with my 18V Bosch !

Thanks for the Crystal Lac comments, I will either use that or Piano Lac. Any preference? Info?

Dave, where's my mail?
I'm Sro Roanry (in Kim Jon Ill's best voice)

Dave, I cannot thank you enough for the hours and hours you have spent developing my project.
QWTL are cool. A local speaker designer who has been doing this for >30 years owns a very HI-end home theater business has let me pick his brain and has offered to let me try out my speakers (when completed) on his many many systems. Wahoo!

Any input is extremely welcome and appreciated.

Thanks, thanks,
Ron

[planet10]

Originally posted by Renron
Dave, where's my mail?

Was i supposed to mail you? Have i got an unansered email in my inbox? (the comment a couple posts up was for Norm)

I cannot thank you enough for the hours and hours you have spent developing my project

Something bothered me about Thor since i 1st read the original article... this thread -- and the info generated for it -- validates my gut feeling. If it hadn't been for that gut feeling, i likely would have never gotten involved, because Thor is not something i'd likely ever build.

Now if we could get the time to write the aXp article "Revisiting the Thor" we could generate a nice donation to the forum. I have a start (which JackinNJ also has). And we'll need pictures & measures.

dave

[dublin78]

Hello

I am curious about your Thor build, as I have always admired this design, and would love to build one if I could find an excuse.

I thought that the Thor was a transmission line design though?

If you are asking questions about maintaining internal volume in a bass reflex or sealed cabinet, this is worrying. If you are asking the same question with regard to a transmission line, have you missed the whole point? In a transmission line the cross-sectional area of the line is crucial and needs to match the design. You can change the shape of the cabinets as much as you like (baffles may need correction), but at the end of the day the cross-sectional area of the line needs to increase/decrease along the line according to the designers specification.

Have I missed something?

[Scottmoose]

Well, the Short Thor box Dave and I designed is not a Bass Reflex cabinet. It's a Mass Loaded Quarter Wave Resonator (Or Mass Loaded Transmission Line). Having said that, yup, cross section needs to be maintained as per the design; MLTLs are no different to other boxes in this respect.

The original Thor is an odd one -seemingly designed as a hybrid line, but because of the nature of the construction / drivers etc it can run into problems, particularly in terms of LF extension.